392 SELECTED NOTES FROM 



EXPLANATION OF PLATES XXII., XXIII., XXIV. 



Plate XXII. 

 Fig. 1. — Arborescent Crystallised Silver. 



,, 2. — Represents a portion of the specimea shown with spines 

 partially seen, in different positions, x 25. 



3. — Figure of Spatangus purpureus from above, to show the 

 form of the shell ; m. indicates the position of the mouth, 

 which is on the under surface ; p. v., position of the vent. 



,, 4. —Base of a large spine, to show the cotyloid cavity, the strung 

 ridge for attachment of muscles which move it, and the 

 rectangular form of the meshes in its calcareous network. 



,, 4a. — Sectional view of the spine, taken at about two-thirds of the 

 length. X 20. 



,, 5. — Truncated column on which the spine is placed, having at its 

 top a smooth, rounded eminence, with depression for attach- 

 ment of a round ligament. x 20. 



,, 6, — Diagram of the parts, in sectional view: — Sp., Spine; 

 rd., rd., Hidge near its base for muscular attachment ; r.l., 

 Round ligament ; ah. m.. Abductor muscle, which, acting at 

 a disadvantage, has its attachment both above and below to 

 a projecting ridge ; ad. m.. Adductor muscle. 



,, 7. — Portion of Seaweed, with Angihinaria dilatata attached. 



,, ^.—Anqninaria anguhia, with polyp partially protruded. 



,, 9. — Head of same, more enlarged, and horse-shoe-shaped chitin- 

 ous lower jaw. 



,, 10. — Another specimen, showing repaired fracture of the neck. 

 ad. m.. Adductor muscle of jaw; ah. m. , Abductor muscle 

 of neck ; r.f., r.f.. Place of repaired fracture. Near the 

 top, towards the right hand side, are some Diatoms, probably 

 Bhahdomina minuta. 



Plate XXIII. 



Eggs op Parasite of Common Fowl. 



Fig. 1. — One of the Eggs, showing the triple coronet of horny cilia 

 surrounding the mouth ; the hexagonal areolation, seldom so 

 strongly expressed as in the figure, the lid, and the glutinous 

 material at the place of attachment. 



,, 2 and 3. — Further illustrate some of these points. 



,, 4. — Illustrating some points in a species cf Scatophaga, S . The 

 figure represents the thorax and abdomen, and is specially 

 designed to show the number and position of the segments 

 composing them, and of the spiracles. 



h., Position of the head ; tx. , Thorax, composed of p.i.cc., 

 Prothorax ; in.s.x., Mesothorax ; m.t.x., Metathorax. The 

 abdominal segments are denoted by the letters a.s., with 1. 

 2, 3, etc., for first, second, and third abdominal segment, and 

 so on ; p.t.x.s., Prothoracic spiracle; m.t.x.s., Metathoracic 



